JVM IR: Avoid direct invokes in callable reference tests

Due to the direct invoke optimization, most callable reference tests
were not generating callable references/lambdas.

compiler/testData/codegen/box/callableReference/function/privateClassMember.kt

@@ -1,7 +1,7 @@
 class A {
     private fun foo() = "OK"
 
-    fun bar() = (A::foo)(this)
+    fun bar() = (A::foo).let { it(this) }
 }
 
 fun box() = A().bar()